1. Field of the Invention
This invention relates to a soft magnetic thin film employed as the core material for magnetic heads. More particularly, it relates to a novel amorphous soft magnetic thin film having a high magnetic flux density and a high electrical resistance.
2. Related Art Statement
In magnetic recording and/or reproducing apparatus, such as video tape recorders or VTRs, it has been tried to improve the image quality, for instance, by elevating the recording density and/or the frequency of record signals. In keeping therewith, high coercive force media such as so-called metal fine powder tapes in which particles of ferromagnetic metals such as Fe, Co or Ni are used as the magnetic particles, or so-called metal thin-film tapes in which the ferromagnetic metal material is directly applied to the base film by evaporation or the similar methods, are being put to practical usage.
It is noted that, with the tendency towards using a high coercive force magnetic recording medium, an increasing demand is naturally raised on using the medium having a high saturation magnetic flux density. The ferrite material, so far used frequently as the head material, has only low saturation magnetic flux density, so that it cannot be used successfully with the high coercive force magnetic recording medium.
Under these circumstances, there has been evolved a composite type magnetic head having its magnetic core formed by a composite structure of ferrite or ceramics and a soft magnetic thin film having a high saturation magnetic flux density, with the magnetic gap being defined by the soft magnetic thin films abutted to each other. There has also been evolved a thin film magnetic head having its magnetic core and coils formed into thin films by the thin film technology, these films being overlapped with the insulating films in between for providing a multilayer structure.
As the soft magnetic thin film, it is known to use for example a magnetic thin film of an Fe-Al-Si type alloy or so-called Sendust having a high saturation magnetic flux density. However, since the magnetic thin film of the Fe-Al-Si type alloy has a electrical resistance .rho. as low as 80 micro-ohm-cm as characteristic of the alloy material, it has a deficiency that its magnetic properties are deteriorated on account of the eddy current loss for the high frequency range, especially in the megaherz range. Such deterioration in the magnetic properties in the high frequency range is unfavorable in view of the recent demand on high density recording or short-wavelength recording.
There are also known in the art metal-metalloid type amorphous alloys, such as Fe-B, Fe-Si-B or Fe-Co-Si-B, or metal-metal type amorphous alloys, such as Co-Zr or Co-Zr-Nb, that may be obtained by liquid or gas-phase rapid cooling methods. These alloys, however, are of the one-phase amorphous structure that may be said to be a homogeneous structure. The saturation magnetic flux density of these alloys is of the order of 10000 Gauss, while an electrical resistance .rho. thereof is indeed larger than that of the Sendust as the crystalline soft magnetic material but amounts to only 150 .mu..OMEGA.-cm at most.
In general, for elevating the saturation magnetic flux density of the conventional soft magnetic thin film, it is necessary to increase the amount of the ferromagnetic metals, such as Fe or Co. The result is the low electrical resistance .rho. of the magnetic thin film. This implies that, with the soft magnetic thin film of the magnetic alloy material, the saturation magnetic flux density and the electrical resistance .rho. are intrinsically contrary to each other in nature, such that it has been difficult to realize the high saturation magnetic flux density and the high electrical resistance simultaneously.